The present invention relates to a display device which utilizes an electron emission into vacuum by applying an electric field.
A color cathode ray tube has been popularly used conventionally as a display device which exhibits excellent properties such as high luminance and high definition. However, along with a demand for high image quality in recent information processing apparatuses and television broadcasting, a demand for a planar display (panel display) which is light-weighted and requires a small-space while ensuring properties such as high luminance and high definition is increased.
As a typical example of such a planar display, a liquid crystal display device, a plasma display device and the like have been commercialized. Further, as the planar display device which can realize the high luminance, various types of panel-type display devices including a display device which makes use of emission of electrons from electron sources into vacuum (hereinafter, referred to as an electron emission type display device or a field emission type display device), an organic EL display which is characterized by its low power consumption and the like are expected to be commercialized soon.
Among such panel-type display devices, as the field emission type display device, a display device having an electron emission structure which is proposed by C. A. Spindt et al., a display device having a metal-insulator-metal (MIM) type electron emission structure, a display device having an electron emission structure which makes use of an electron emission phenomenon due to a quantum theory tunneling effect (also referred to as a surface conductive type electron source), a display device which makes use of an electron emission phenomenon possessed by a diamond film, a graphite film or a carbon nanotube and the like have been known.
The field emission type display device includes a back panel which forms cathode lines having field emission type electron sources and control electrodes on an inner surface thereof and a front panel which forms anodes and phosphors on an inner surface which faces the back panel in an opposed manner, wherein the display device is constituted by laminating both panels while inserting a sealing frame between inner peripheries of both panels and by evacuating the inside thereof. Further, to hold a distance between the back panel and the front panel at a given value, distance holding members are provided between the back panel and the front panel at positions away from the above-mentioned cathode lines and the control electrodes.
The back panel includes a plurality of cathode lines having electron sources and the control electrodes on a back substrate which is preferably made of glass, alumina or the like. A large number of cathode lines extend in one direction on the back substrate and are arranged in parallel in another direction. The control electrodes are arranged adjacent to the cathode lines. A large number of control electrodes extend in the above-mentioned another direction and are arranged in parallel in the above-mentioned one direction. Pixels are formed at crossing portions between the cathode lines (electron sources provided to cathode lines) and the control electrodes.
Then, an emission quantity (including ON and OFF) of electrons from the electron source is controlled in response to the potential difference between the cathode lines and the control electrodes. On the other hand, the front panel has the anodes and the phosphors on a front substrate which is formed of a light-transmitting material such as glass. The inside sealed by the sealing frame is evacuated into vacuum of 10−5 –10−7 Torr, for example. The control electrode has electron passing holes at each crossing portion between the cathode lines and the control electrode, which allows electrons emitted from the electron source of the cathode line to transmit therethrough toward the anode side. The above-mentioned electron sources are constituted of carbon nanotube (CNT), diamond-like carbon (DLC) or other field emission cathodes, for example.
However, although the cathode lines are arranged in parallel with a gap therebetween, this gap has been set equal conventionally. Accordingly, to ensure a sufficient spaces for forming the distance holding members, it has been necessary to increase the gap between the respective cathode lines. Further, when plate-like control electrodes which are constituted of plate members are used as the control electrodes, protrusions which are brought into contact with the back substrate are formed at portions away from back faces of the plate-like control electrodes, that is, cathode lines of back substrate side, and the distance holding members are positioned at upper surfaces of the control electrodes which correspond to these protrusions. However, in this case, an extremely accurate operation is necessary to achieve the positioning or the alignment of the protrusions of the plate-like control electrodes and the cathode lines.